linux-kernel - [PATCH v3] hwmon: (k10temp) Enable AMD3255 Proc to show negative temperature

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Date:   Mon, 19 Jun 2023 11:54:14 -0500
From:   Baskaran Kannan <Baski.Kannan@....com>
To:     <Mario.Limonciello@....com>, <babu.moger@....com>,
        <baski.kannan@....com>, <clemens@...isch.de>, <jdelvare@...e.com>,
        <linux@...ck-us.net>, <linux-hwmon@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Baskaran Kannan <Baski.Kannan@....com>
Subject: [PATCH v3] hwmon: (k10temp) Enable AMD3255 Proc to show negative temperature

Industrial processor i3255 supports temperatures -40 deg celcius
to 105 deg Celcius. The current implementation of k10temp_read_temp
rounds off any negative
temperatures to '0'. To fix this, the following changes have been made.
Added a flag 'disp_negative' to struct k10temp_data to support
AMD i3255 processors. Flag 'disp_negative' is set if 3255 processor
is found during k10temp_probe.  Flag 'disp_negative' is used to determine
whether to round off negative temperatures to '0' in k10temp_read_temp.

Signed-off-by: Baskaran Kannan <Baski.Kannan@....com>
---
 drivers/hwmon/k10temp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/k10temp.c b/drivers/hwmon/k10temp.c
index 7b177b9fbb09..2613420d43ff 100644
--- a/drivers/hwmon/k10temp.c
+++ b/drivers/hwmon/k10temp.c
@@ -86,6 +86,7 @@ struct k10temp_data {
 	u32 show_temp;
 	bool is_zen;
 	u32 ccd_offset;
+	bool disp_negative;
 };
 
 #define TCTL_BIT	0
@@ -204,12 +205,12 @@ static int k10temp_read_temp(struct device *dev, u32 attr, int channel,
 		switch (channel) {
 		case 0:		/* Tctl */
 			*val = get_raw_temp(data);
-			if (*val < 0)
+			if (*val < 0 && !data->disp_negative)
 				*val = 0;
 			break;
 		case 1:		/* Tdie */
 			*val = get_raw_temp(data) - data->temp_offset;
-			if (*val < 0)
+			if (*val < 0 && !data->disp_negative)
 				*val = 0;
 			break;
 		case 2 ... 13:		/* Tccd{1-12} */
@@ -405,6 +406,9 @@ static int k10temp_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	data->pdev = pdev;
 	data->show_temp |= BIT(TCTL_BIT);	/* Always show Tctl */
 
+	if (boot_cpu_data.x86 == 0x17 && boot_cpu_data.x86_model < 0x8)
+		data->disp_negative = true;
+
 	if (boot_cpu_data.x86 == 0x15 &&
 	    ((boot_cpu_data.x86_model & 0xf0) == 0x60 ||
 	     (boot_cpu_data.x86_model & 0xf0) == 0x70)) {
-- 
2.25.1